Simplifying a complex subject. Child psychology is required for college level psych and elementary education majors. It is a complex subject that can include developmental psychology, biology, sociological psychology, and various schools of theory and therapies. The only sources of information about this complex subject are long, expensive textbooks. Until now. This, the first trade book to give a detailed, easy to understand explanation of the subject. ? Age-by-age discussion of the psychological development of children.